Gravitational waves from quasinormal modes of a class of Lorentzian wormholes

TL;DR

This paper investigates gravitational wave signatures of Lorentzian wormholes in scalar-tensor theories, proposing how their unique quasinormal modes, especially breathing modes, could be detected to distinguish them from black holes.

Contribution

It introduces a method to identify Lorentzian wormholes via their scalar quasinormal modes in gravitational wave data, linking observations to modified gravity theories and extra dimensions.

Findings

Breathing modes depend on wormhole parameters and can be distinguished from black holes.

Detection of scalar modes could provide evidence for modified gravity and extra dimensions.

Wormhole properties can be inferred from gravitational wave signatures in future observations.

Abstract

Quasinormal modes of a two-parameter family of Lorentzian wormhole spacetimes, which arise as solutions in a specific scalar-tensor theory associated with braneworld gravity, are obtained using standard numerical methods. Being solutions in a scalar-tensor theory, these wormholes can exist with matter satisfying the Weak Energy Condition. If one posits that the end-state of stellar-mass binary black hole mergers, of the type observed in GW150914, can be these wormholes, then we show how their properties can be measured from their distinct signatures in the gravitational waves emitted by them as they settle down in the post-merger phase from an initially perturbed state. We propose that their scalar quasinormal modes correspond to the so-called breathing modes, which normally arise in gravitational wave solutions in scalar-tensor theories. We show how the frequency and damping time of these modes depend on the wormhole parameters, including its mass. We derive the mode solutions and use them to determine how one can measure those parameters when these wormholes are the endstate of binary black hole mergers. Specifically, we find that if a breathing mode is observed in LIGO-like detectors with design sensitivity, and has a maximum amplitude equal to that of the tensor mode that was observed of GW150914, then for a range of values of the wormhole parameters, we will be able to discern it from a black hole. If in future observations we are able to confirm the existence of such wormholes, we would, at one go, have some indirect evidence of a modified theory of gravity as well as extra spatial dimensions.